This invention relates to a lock core that is manually removable by use of a key, for use in a lock cylinder, doorknob, or other core receptacle defining a core-receiving opening or chamber.
A key-removable lock core of the type shown, for example, in FIGS. 1-7 of Frank E. Best's U.S. Pat. No. 3,206,958 (the disclosure of which is incorporated herein by reference in its entirety) has been known since the 1920's and have been widely sold and used in a standard configuration and size so as to be readily interchangeable and renewable in the same lock mechanisms. Such standard lock core includes a core body of figure-8 cross section with body a key plug and a full-length thin-walled sleeve within its bottom lobe, the sleeve being rotatable through a limited angle to retract a core-retainer lug thereon. An axial series of pin tumbler barrels extend through the pin tumbler housing formed by the top lobe of the core body, through a thickened portion of the sleeve contained in a broached recess in such upper lobe, and into the key plug. This arrangement forms a full-length operating shear line at the interface between the key plug and the sleeve, and a full-length control shear line at the interface between the thickened portion of the sleeve and the upper lobe of the core body. An operating key will align the tumblers for shear at the operating shear line to allow the key plug to be rotated, while a control key will align the tumblers for shear at the control shear line to allow the sleeve and the key plug together to be rotated to move the retaining lug on the sleeve between a retracted position within the figure-8 profile of the core and a projected position in which such lug is engaged behind a rearward-facing shoulder in the core receptacle to retain the core in such receptacle.
Walter E. Best's et al. U.S. Pat. No. 4,424,693 (the disclosure of which is incorporated herein by reference in its entirety) shows another type of key-removable lock core for a lock chamber of figure-8 cross section having a short cylindrical key plug housing fitting the lower lobe of the chamber and a pin tumbler housing containing a series of pin tumbler barrels, two of which are in an extension beyond the key plug housing. A key plug is contained in such housing and a control sleeve aligned with such housing beneath the extension and having pin tumbler bores aligned with said two barrels. Side faces on the pin tumbler housing and spaced from the chamber side wall provide clearance on one side for a retaining lug on the control sleeve retractable into such clearance from core-retaining engagement behind a shoulder in the chamber, and clearance on the other side for a stop lug. An operating key aligns tumblers in all barrels for shear movement at an operating shear line at the outer surface of the key plug. A control key aligns tumblers in the two extension-contained barrels for shear movement at a control shear line at the outer surface of the control sleeve, and tumblers in the other barrels for shear movement at the operating shear line, to permit rotation of the sleeve to retract its retaining lug. The pin tumbler housing may have flat sides which define the lug clearances or may be cylindrical and have clearance recesses cut in it with end faces which ride against the lugs. The core may have a separate face plate, or the pin tumbler housing may itself form the front face of the core.
Peter H. Field's et al. U.S. Pat. No. 6,382,006 (the disclosure of which is incorporated herein by reference in its entirety) shows another type of key-removable lock core for a lock chamber of figure-8 cross section having an extended-length control key that engages a control tumbler, unreachable with the operating key. The control key engages the control tumbler across the operating shear line, while freeing movement of the sleeve at the control shear line.
In the above described key-removable lock cores, and other known and described conventional key-removable lock cores, an operating key aligns the tumblers for shear at the operating shear line to allow the key plug to be rotated, while a separate control key aligns the tumblers for shear at the control shear line, to allow the sleeve and the key plug together to be rotated to move the retaining lug on the sleeve between a retracted position within the figure-8 profile of the core and a projected position in which the lug is engaged behind a rearward-facing shoulder in the core receptacle to retain the core in the receptacle.